Embodiments of the present invention generally relate to leadless implantable medical devices (LIMDs) and more particularly to temporary LIMDs that are implanted for a short period of time.
Recently, it has been proposed to utilize small sized devices configured for intra-cardiac implant. These devices, termed leadless implantable medical devices (LIMDs) are typically characterized by the following features: they are devoid of leads that pass out of the heart to another component, such as a pacemaker outside of the heart; they include electrodes that are affixed directly to the “can” of the device or to extensions of the device; and the device is capable of pacing and sensing in the chamber of the heart where it is implanted.
LIMDs that have been proposed thus far offer limited functional capability. These LIMDs are able to sense in one chamber and deliver pacing pulses in that same chamber, and thus offer single chamber functionality. For example, an LIMD device that is located in the right atrium offers AAI mode functionality. An AAI mode LIMD can only sense in the right atrium, pace in the right atrium and inhibit pacing function when an intrinsic event is detected in the right atrium within a preset time limit. Similarly, an LIMD that is located in the right ventricle would be limited to offering WI mode functionality. A WI mode LIMD can only sense in the right ventricle, pace in the right ventricle and inhibit pacing function when an intrinsic event is detected in the right ventricle within a preset time limit. More recently, LIMDs have been proposed that afford dual chamber pacing/sensing capability (DDD mode) along with other features, such as rate adaptive pacing.
LIMDs are being considered initially for chronic pacing patients, such as with current indications for VVIR pacing. However, another possible use for the LIMD is for temporary use, such as in the order of a few months or even less than 30 days (e.g., for patients needing peri-operative, but not chronic, pacing). The indications for such temporary LIMDs would include patients who are currently indicated for temporary pacing using an external pacer, for example patients recovering from heart surgery. As another example, it is known that a potential complication of surgical aortic valve replacement is sudden death in the month following surgery. However, the risk of sudden death could be mediated by offering a device that can support pacing during a time period when the patient may experience heart block.
One of the challenges with leadless implantable medical devices will be explant, whether for battery depletion, lack of need, infection or otherwise. Various systems are being developed to capture the proximal end of a leadless pacemaker and retrieve it. See for example Khairkhahan 2012/0165827 (Nanostim).
It is known to anchor a temporary pacemaker or intravascular defibrillator with a tether inside a vein. For example, Ostroff 2009/0082828 shows a tether anchoring the leadless pacemaker to an intraluminal stent in the inferior vena cava. An intravascular anchor with tether is also shown in Ransbury 2011/0071585.
However, conventional approaches experience certain limitations. For example, to explant conventional LIMDs, a separate extraction tool must be introduced and independently steered or manipulated along the patient's vasculature system into the heart and to a chamber in which the LIMD is implanted. The extraction tool must be independently guided by the physician. It may be difficult to align and connect the extraction tool with the LIMD. This alignment process may become unduly time consuming. Also, the physician typically utilizes a fluoroscopy system, CT system and the like to watch the position and movement of the extraction tool relative to the LIMD. Hence, the patient is exposed to a certain amount of radiation during the LIMD extraction process. The amount of radiation will vary based upon the amount of time needed, and number of images taken, in connection with attaching the extraction tool to the LIMD, detaching the LIMD from the heart tissue and extracting the LIMD.
A need remains for an extraction system and method that is efficient, not time consuming, and reduces a physician's need for fluoroscopy or CT images of the patient.